Molecular layer and method of forming the same

ABSTRACT

A molecular layer includes a Langmuir-Blodgett (LB) film of a molecule connected to a plurality of active device molecules, the molecule having a moiety with first and second connecting groups at opposed ends of the moiety. Each of the plurality of active device molecules includes a switching moiety, a self-assembling connecting group at one end of the switching moiety, and a linking group at an opposed end of the moiety. One or more defect site(s) exist between the plurality of active device molecules. A respective number of the first connecting groups of the LB film are connected to the plurality of active device molecules via at least some of the linking groups such that the LB film covers the plurality of active device molecules and the one or more defect site(s).

BACKGROUND

The present invention relates generally to molecular electronics, andmore particularly to a molecular layer formed by Langmuir-Blodgett (LB)and self-assembling monolayer (SAM) methods.

Molecular devices comprising two electrodes (for example, a bottomelectrode and a top electrode) and a molecular switching layer or filmat the junction of the two electrodes are known. Such devices may beuseful, for example, in the fabrication of devices based on electricalswitching, such as molecular wire crossbar interconnects for signalrouting and communications, molecular wire crossbar memory, molecularwire crossbar logic employing programmable logic arrays, multiplexers ordemultiplexers for molecular wire crossbar networks, molecular wiretransistors, and the like. Such devices may further be useful, forexample, in the fabrication of devices based on optical switching, suchas displays, electronic books, rewritable media, electrically tunableoptical lenses, electrically controlled tinting for windows and mirrors,optical crossbar switches (for example, for routing signals from one ofmany incoming channels to one of many outgoing channels), and the like.

Typically, the molecular switching layer or film comprises an organicmolecule that, in the presence of an electrical (E) field, switchesbetween two or more energetic states, such as by an electrochemicaloxidation or reduction (redox) reaction or by a change in the band gapof the molecule induced by the applied E-field.

It is important to form a good electrical contact between the electrodeand the molecular switching layer in order to fabricate operativemolecular devices. Molecules with special chemical end groups are ableto form direct chemical bonds with metal or semiconductor electrodes toform a self-assembled monolayer (SAM), which may have a good electricalcontact with an electrode(s). However, this self-assembled molecularlayer formed on the surface of the electrode may generally be prone to ahigh density of defects. If a second electrode is formed on themolecular layer, then an electrical short may occur between the firstand second electrode through the defects in the self-assembled molecularlayer.

The formation of Langmuir-Blodgett (LB) layers or films employingswitching molecules has been attempted because such layers or films aregenerally much denser than SAM films. Further, LB layers or films haverelatively low defect densities compared to SAM films. However, it hasproven to be a significant challenge to effectively bond LB films to theelectrode substrate. As such, if the LB film is not sufficiently bondedto the electrode(s), then poor electrical contact may result.

As such, there is a need for providing a high density molecularswitching layer on an electrode(s), which layer also bonds well with theelectrode. Further, there is a need for reducing or substantiallyeliminating the electrical short circuit problems potentially associatedwith molecular electronic devices.

SUMMARY

The present invention substantially solves the drawbacks enumeratedabove by providing a molecular layer including a Langmuir-Blodgett (LB)film of a molecule connected to a plurality of active device molecules.The molecule has a moiety with first and second connecting groups atopposed ends of the moiety. Each of the plurality of active devicemolecules includes a switching moiety, a self-assembling connectinggroup at one end of the switching moiety, and a linking group at anopposed end of the moiety. One or more defect site(s) exist between theplurality of active device molecules. A respective number of the firstconnecting groups of the LB film are connected to at least some of theplurality of active device molecules via the linking groups such thatthe LB film covers the plurality of active device molecules and the oneor more defect site(s).

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, features and advantages will become apparent by reference tothe following detailed description and drawings, in which like referencenumerals correspond to similar, though not necessarily identicalcomponents. For the sake of brevity, reference numerals having apreviously described function may not necessarily be described inconnection with subsequent drawings in which they appear.

FIG. 1A is a schematic representation of two crossed wires, with atleast one molecule at the intersection of the two wires;

FIG. 1B is a perspective elevational view, depicting the crossed-wiredevice shown in FIG. 1 a;

FIG. 2 is a schematic representation of a two-dimensional array ofswitches, depicting a 6×6 crossbar switch;

FIGS. 3A-3G is a schematic flow diagram depicting an embodiment of amethod of forming a molecular layer between two electrodes; and

FIGS. 4A-4H is a schematic flow diagram depicting an alternateembodiment of a method of forming a molecular layer between twoelectrodes, including the deposition of a polymer film on the molecularlayer.

DETAILED DESCRIPTION

Embodiments of the present invention advantageously use a novel conceptof providing a molecular layer, which may act as a protective layer.This novel concept takes advantage of the advantageous qualities ofself-assembly techniques (SAM) (e.g. good electrical contact due tochemical bonding) and Langmuir-Blodgett (LB) deposition (e.g. low defectdensity). The concept further substantially eliminates problems that mayin some instances be associated with these techniques.

The method according to embodiments of the present invention providesorienting an LB film that may be dense and highly uniform on a molecularfilm such that the LB film acts as a barrier between the molecular filmand any subsequently deposited metal.

Referring now to FIGS. 1A-1B, a crossed wire switching device 10includes two wires 12, 14, each either a metal and/or semiconductorwire, that are crossed at some substantially non-zero angle. Disposedbetween wires 12, 14 is a layer 16 of molecules or molecular compounds,denoted R. The particular molecules (active device molecules) 18 thatare sandwiched at the intersection (also interchangeably referred toherein as a junction) of the two wires 12, 14 are identified as switchmolecules R_(S).

There are generally two primary methods of operating such switches 10,depending on the nature of the switch molecules 18. The molecularswitching layer 16 includes a switch molecule 18 (for example, anorganic molecule) that, in the presence of an electrical (E) field,switches between two or more energetic states, such as by anelectrochemical oxidation or reduction (redox) reaction or by a changein the band gap of the molecule induced by the applied E-field.

In the former case, when an appropriate voltage is applied across thewires 12, 14, the switch molecules R_(S) are either oxidized or reduced.When a molecule is oxidized (reduced), then a second species is reduced(oxidized) so that charge is balanced. These two species are then calleda redox pair. One example of this device would be for one molecule to bereduced, and then a second molecule (the other half of the redox pair)would be oxidized. In another example, a molecule is reduced, and one ofthe wires 12, 14 is oxidized. In a third example, a molecule isoxidized, and one of the wires 12, 14 is reduced. In a fourth example,one wire 12, 14 is oxidized, and an oxide associated with the other wire14, 12 is reduced. In such cases, oxidation or reduction may affect thetunneling distance or the tunneling barrier height between the twowires, thereby exponentially altering the rate of charge transportacross the wire junction, and serving as the basis for a switch.Examples of molecules 18 that exhibit such redox behavior includerotaxanes, pseudo-rotaxanes, and catenanes; see, e.g., U.S. Pat. No.6,459,095, entitled “Chemically Synthesized and Assembled ElectronicDevices”, issued Oct. 1, 2002, to James R. Heath et al, the disclosureof which is incorporated herein by reference in its entirety.

Further, the wires 12, 14 may be modulation-doped by coating theirsurfaces with appropriate molecules—either electron-withdrawing groups(Lewis acids, such as boron trifluoride (BF₃)) or electron-donatinggroups (Lewis bases, such as alkylamines) to make them p-type or n-typeconductors, respectively. FIG. 1B depicts a coating 20 on wire 12 and acoating 22 on wire 14. The coatings 20, 22 may be modulation-dopingcoatings, tunneling barriers (e.g., oxides), or other nano-scalefunctionally suitable materials. Alternatively, the wires 12, 14themselves may be coated with one or more R species 16, and where thewires cross, R_(S) 18 is formed. Or yet alternatively, the wires 12, 14may be coated with molecular species 20, 22, respectively, for example,that enable one or both wires 12, 14 to be suspended to form colloidalsuspensions, as discussed below. Details of such coatings are providedin above-referenced U.S. Pat. No. 6,459,095.

In the latter case, examples of molecule 18 based on field inducedchanges include E-field induced band gap changes, such as disclosed andclaimed in patent application Ser. No. 09/823,195, filed Mar. 29, 2001,published as Publication No. 2002/0176276 on Nov. 28, 2002, whichapplication is incorporated herein by reference in its entirety.Examples of molecules used in the E-field induced band gap changeapproach include molecules that evidence molecular conformation changeor an isomerization; change of extended conjugation via chemical bondingchange to change the band gap; or molecular folding or stretching.

Changing of extended conjugation via chemical bonding change to changethe band gap may be accomplished in one of the following ways: chargeseparation or recombination accompanied by increasing or decreasing bandlocalization; or change of extended conjugation via charge separation orrecombination and λ-bond breaking or formation.

The formation of micrometer scale and nanometer scale crossed wireswitches 10 uses either a reduction-oxidation (redox) reaction to forman electrochemical cell or uses E-field induced band gap changes to formmolecular switches. In either case, the molecular switches typicallyhave two states, and may be either irreversibly switched from a firststate to a second state or reversibly switched from a first state to asecond state. In the latter case, there are two possible conditions:either the electric field may be removed after switching into a givenstate, and the molecule will remain in that state (“latched”) until areverse field is applied to switch the molecule back to its previousstate; or removal of the electric field causes the molecule to revert toits previous state, and hence the field must be maintained in order tokeep the molecule in the switched state until it is desired to switchthe molecule to its previous state.

Color switch molecular analogs, particularly based on E-field inducedband gap changes, are also known; see, e.g., U.S. application Ser. No.09/844,862, filed Apr. 27, 2001.

Referring now to FIG. 2, the switch 10 may be replicated in atwo-dimensional array to form a plurality or array 24 of switches 10 toform a crossbar switch. FIG. 2 depicts a 6×6 array 24. However, it is tobe understood that the embodiments herein are not to be limited to theparticular number of elements, or switches 10, in the array 24. Accessto a single point, e.g., 2 b, is done by impressing voltage on wires 2and b to cause a change in the state of the molecular species 18 at thejunction thereof, as described above. Thus, access to each junction isreadily available for configuring those that are pre-selected. Detailsof the operation of the crossbar switch array 24 are further discussedin U.S. Pat. No. 6,128,214, entitled “Molecular Wire Crossbar Memory”,issued on Oct. 3, 2000, to Philip J. Kuekes et al., which isincorporated herein by reference in its entirety.

An embodiment of the molecular layer 21 (depicted in FIGS. 3E & 3G)includes a Langmuir-Blodgett (LB) film of a molecule connected to aplurality of active device molecules. The molecule includes a molecularswitching moiety having first and second connecting groups at opposedends of the moiety while each of the plurality of active devicemolecules includes a switching moiety, a self-assembling connectinggroup at one end of the switching moiety, and a linking group at anopposed end of the switching moiety. The molecular layer 21 also has atleast one defect site between the plurality of active device molecules.A respective number of the first connecting groups of the LB film areconnected to the plurality of active device molecules via the linkinggroups such that the LB film covers the plurality of active devicemolecules and the at least one defect site.

Referring now to FIGS. 3A through 3G, a method of forming a molecularlayer 21 according to an embodiment is as follows.

Generally, FIGS. 3A through 3D depict the formation of both aself-assembled molecular film 29 (FIGS. 3A and 3B) and an LB film 30(FIGS. 3C and 3D). The self assembled molecular film 29 is formed from aplurality of active device molecules 18 connected to a substrate 25, theactive device molecules 18 each having a molecular switching moiety (MD)26 with a linking group (LG) 27 and a self assembled connecting group(SACG) 28 attached at opposed ends of the moiety (MD) 26. The selfassembled molecular film 29 also has at least one defect site 31 therein(as seen in FIG. 3B).

The LB film 30 is made from a plurality of molecules 18′ formed on aninterface 36 between an organic solvent(s)/air and water, each of themolecules 18′ having a molecular switching moiety (MD1) 26′ with firstand second connecting groups (CG1) 32, (CG2) 34 attached at opposed endsof the moiety (MD1) 26′. In an alternate embodiment, moiety (MD1) 26′ isnot a switching moiety; in this embodiment, the LB film 30 mainly servesas a protective layer for the SAM film 29, for example by serving as aninsulating portion to substantially aid in preventing electricalshorting, metal penetration, undesirable chemical reactions, or thelike.

More specifically, FIGS. 3A and 3B depict active device molecule(s) 18chemically bonded to a surface of the substrate 25 to form aself-assembled molecular film 29. Chemically bonding the active devicemolecules 18 to the substrate 25 may be accomplished by a self-assembledmono-layer (SAM) process. Using this process, self-assembling connectinggroups (SACG) 28 of the active device molecules 18 bond to the substrate25 surface.

It is to be understood that the substrate 25 may be made of any suitableconductive or semi-conductive material. In an embodiment, the substrate25 is a bottom electrode 23 made of noble metals (e.g. Au, Pt, Ag, Cu,alloys of these metals, or the like). It is to be understood that in anoptical application, the substrate 25 may be a non-electrode material ora transparent electrode, such as indium tin oxide (ITO).

In an embodiment, the active device molecule 18 includes a switchingmoiety (MD) 26 having a linking group (LG) 27 and the previouslymentioned self-assembling connecting group (SACG) 28 at opposed endsthereof.

The molecular switching moiety (MD) 26, (MD1) 26′ is an opticallyswitchable molecular functional unit and/or an electrically switchablemolecular functional unit. It is to be understood that the switchingmoiety (MD) 26, (MD1) 26′ may be any suitable moiety, however, in anembodiment, the moiety (MD) 26, (MD1) 26′ includes at least one ofsaturated hydrocarbons, unsaturated hydrocarbons, substitutedhydrocarbons, heterocyclic systems, organometallic complex systems, ormixtures thereof.

In an embodiment, the switching moiety (MD) 26, (MD1) 26′ includes amoiety that, in the presence of an electric field, undergoes oxidationor reduction, and/or experiences a band gap change. In one embodiment,the switching moiety (MD) 26, (MD1) 26′ undergoes oxidation or reductionand includes at least one of rotaxanes, pseudo-rotaxanes, catenanes, andmixtures thereof. In another embodiment, the switching moiety (MD) 26,(MD1) 26′ undergoes a band gap change in the presence of an externalelectrical field, this is described in U.S. Pat. No. 6,674,932 grantedto Zhang et al. on Jan. 6, 2004, the specification of which is herebyincorporated herein by reference in its entirety.

The linking group (LG) 27 may be bonded to one end of the switchingmoiety (MD) 26 such that it is adapted to bond to the LB film 30 (shownin FIG. 3E). It is to be understood that the linking group (LG) 27 maybe, but is not limited to at least one of multivalent hetero atomsselected from the group consisting of C, N, O, S, and P; functionalgroups containing the hetero atoms and selected from the groupconsisting of NH₂, NH-alkyl, NH-acyl, and NH-aryl; pyridine; substitutedpyridines; heterocyclic compounds including at least one nitrogen atom;carboxylic acids; derivatives thereof (non-limitative examples of whichinclude carboxylic esters, amides, nitriles, or the like); sulfuricacids; phosphoric acids; saturated hydrocarbons; unsaturatedhydrocarbons; heterocyclic systems; amines; alkyl amines; and mixturesthereof.

The self-assembling connecting group (SACG) 28 may be bonded to theopposed end of the switching moiety (MD) 26, such that it is capable ofbonding to the substrate 25 surface. Examples of suitableself-assembling connecting groups (SACG) 28 include, but are not limitedmultivalent hetero atoms selected from the group consisting of C, N, O,S, and/or P; functional groups containing the hetero atoms and selectedfrom the group consisting of SH, S-acyl, S—S-alkyl, OH, NH₂, NH-alkyl,NH-aryl, NH-acyl; heterocyclic compounds; pyridine; substitutedpyridines (non-limitative examples of which include amino substitutedpyridines, such as N,N-dimethylamino pyridine); carboxylic acids;derivatives thereof (non-limitative examples of which include carboxylicesters, amides, nitriles, or the like); amines; alkyl amines; ormixtures thereof.

Upon bonding the active device molecules 18 to the substrate 25 via aSAM process, the self-assembled molecular film 29 is formed. Due in partto the SAM process, the self-assembled molecular film 29 may be aloosely packed mono-layer film that contains one or more defect sites 31that may in some instances cause short circuits when electrical contacts(e.g. top electrodes) are deposited on the film 29.

Referring now to FIGS. 3C and 3D together, an aqueous environmentcontains a molecule 18′ with a molecular switching moiety (MD1) 26′having a first connecting group (CG1) 32 and a second connecting group(CG2) 34 attached to opposed ends of the moiety (MD1) 26′.

In an embodiment, the molecule 18′ is an organic molecule, and themolecular switching moiety (MD1) 26′ (as previously described) is anoptically switchable molecular functional unit and/or an electricallyswitchable molecular functional unit.

The first and second connecting groups (CG1, CG2) 32, 34 may behydrophilic or hydrophobic, as long as at least one (CG1, CG2) 32, 34 issubstantially hydrophilic while the other (CG2, CG1) 34, 32 issubstantially hydrophobic. Examples of suitable connecting groups (CG1,CG2) 32, 34 include, but are not limited to multivalent hetero atomsselected from the group consisting of C, N, O, S, and P; functionalgroups containing the hetero atoms and SH; OH; NH₂; NH-alkyl; NH-aryl;NH-acyl; pyridine; saturated hydrocarbons; unsaturated hydrocarbons;heterocyclic compounds including at least one nitrogen atom;heterocyclic systems; carboxylic acids; derivatives thereof(non-limitative examples of which include carboxylic esters, amides,nitriles, or the like); amines; alkyl amines; sulfuric acids; phosphoricacids; and mixtures thereof.

While the first connecting group (CG1) 32 is adapted to bond to thelinking group (LG) 27 (as described hereinbelow), it is to be understoodthat either the first or the second connecting group (CG1, CG2) 32, 34may be adapted to bond to the linking group (LG) 27 of theself-assembled molecular film 29.

A Langmuir-Blodgett (LB) film 30 of the molecule 18′ is formed on aninterface 36 between an organic solvent(s)/air and water, the film 30being depicted by the plurality of molecules 18′ shown in FIG. 3D. Theorganic solvent(s) is above the water, and in some instances mayvolatilize quickly; as such what was an interface 36 between water andorganic solvent(s) may become an interface 36 between water and air.Thus, it is to be understood that interface 36 as defined herein may bea water/solvent interface 36 and/or a water/air interface 36.

The method further includes connecting the LB film 30 to theself-assembled molecular film 29. It is contemplated that one of thefirst and second connecting groups (CG1, CG2) 32, 34 of the molecule 18′may be chemically or physically bonded to one or more of the linkinggroups (LG) 27 of the active device molecules 18 in the self-assembledmolecular film 29. In an embodiment and as shown in FIGS. 3E and 3F, thefirst connecting group(s) (CG1) 32 is adapted to bond and does bond toat least some of the linking groups (LG) 27 of the self assembledmolecular film 29.

Connecting the LB film 30 to the self-assembled molecular film 29 may beaccomplished by either a direct connection (FIG. 3E) or by an indirectconnection (FIGS. 3E and 3F together). FIG. 3F illustrates anintermediate step where the LB film 30 is deposited on, but notconnected to the self-assembled molecular film 29.

It is to be understood that the connection between the LB film 30 andthe self-assembled molecular film 29 may occur via physical and/orchemical bonding.

Examples of physical bonding include, but are not limited to hydrogenbonding and van der Waals force. In a non-limitative embodiment usinghydrogen bonding, at least one of the linking group (LG) 27 and thefirst connecting group (CG1) 32 includes either one of —NH, OH, and SH,or a functional group containing at least one of —NH, OH, and SH. Theother of the linking group (LG) 27 and the first connecting group (CG1)32 may be, but is not limited to, one of Cl, F, Br, I, —OH, —SH, —NH,—NHOH, —NHNH₂, ethers, thio-ethers, esters, thio-esters, ureas,carboxylic acids, amides, amines, ketones, aldehydes, nitriles, —NHCNH,a heterocyclic system containing at least one of the followinghetero-atoms: N, O, and S, or mixtures thereof.

The bonding between the linking group (LG) 27 and the first connectinggroup (CG1) 32 via a van der Waals force may be established when both ofthe groups 27, 32 are hydrocarbons (either saturated or unsaturated),substituted hydrocarbons, ethers, thio-ethers, esters, thio-esters or aheterocyclic system containing at least one of the followinghetero-atoms: N, O, and S.

It is to be understood that chemical bonding may be one of ionicbonding, covalent bonding and coordination bonding. Covalent bonding maybe accomplished by one of oxidative cross-linking, heat- orphoto-initiated cross-linking, substitution reaction, esterification andamide-formation. Examples of the bonds between the linking group (LG) 27and the first connecting group (CG1) 32 include, but not limited to, oneof the following: —S—S—, —CH₂CHR—CHR′CH₂, —C≡C—C≡C, —CHR—O—CHR′—,—CHR—S—CHR′—, —CHR—NH—CHR′—, —CHR—NR″—CHR′—, and —COO—CHR—. Othersuitable examples of the linking group (LG) 27 and the first connectinggroup (CG1) 32 include, but are not limited to —COOH, —OH, —SH, —NHR,—CHR—I, —CHR—Br, —CHR—Cl, —CHR—O—SO₃CF₃, —CHR—O—SO₃C₆H₄CH₃, —C≡C—H, or avinyl group. It is to be understood that the R, R′ and R″ may be any oneof hydrogen, alkyls and aryl groups.

Ionic bonding between the linking group (LG) 27 and the first connectinggroup (CG1) 32 may be established by an acid-base reaction (ionizationreaction). In this embodiment, one of the linking group (LG) 27 and thefirst connecting group (CG1) 32 is at least one of, for example, —CO₂H,—SO₃H, and —PO₃H; and the other of the linking group (LG) 27 and thefirst connecting group (CG1) 32 is an amine or an alkyl amine, forexample.

FIG. 3E depicts the formed molecular layer 21 on the substrate 25. It isto be understood that the structure of the molecular layer 21 is suchthat the LB film covers the plurality of active device molecules 18 andthe one or more defect site(s) 31. It is believed, without being boundto any theory, that the LB film 30 may be adapted to protect theplurality of active device molecules 18 and the at least one defect site31 from potential problems (e.g. metal penetration, electrical shortingand chemical reaction) associated with the addition of a metal layer(e.g. top electrode 38 shown in FIG. 3G) or the surrounding environment.

Referring now to FIG. 3G, an embodiment of the method may furtherinclude depositing a top electrode or substrate 38 on the LB film 30. Inan embodiment, one of the first connecting group 32 or the secondconnecting group 34 is a connecting unit between the formed molecularlayer 21 and the top electrode or substrate 38. It is to be understoodthat the substrate 38 may be either an electrode or a non-electrode,depending on the application. It is to be further understood that thesubstrate 38 may be hydrophilic or hydrophobic. As such, firstconnecting group 32 or second connecting group 34 will be more attractedto the substrate 38, depending upon the hydrophilicity/hydrophobicity ofthe substrate 38 and of the group 32, 34.

The top electrode or substrate 38 may be made of noble metals (e.g. Au,Pt, Ag, Cu, alloys of these metals, or the like). It is to be understoodthat any suitable deposition technique may be used, and in anembodiment, the top electrode or substrate 38 is deposited via anevaporative deposition method. Without being bound to any theory, it isbelieved that the substantially dense and uniform LB film 30advantageously substantially prevents metal penetration duringevaporative metal deposition when the top electrode or substrate 38 isformed and/or when subsequent metal diffusion occurs. The LB film 30 mayalso advantageously prevent a chemical reaction between the activedevice molecules 18 and the top electrode or substrate 38 or otherenvironmental contaminants.

FIGS. 4A through 4H depict a similar embodiment of the method previouslydescribed in reference to FIGS. 3A through 3G, with an additional steptherein. FIGS. 4A through 4F illustrate the formation of the molecularlayer 21 by chemically bonding the active device molecules 18 to thesurface of a substrate 25 to form the self-assembled molecular film 29,forming an LB film 30, and connecting (either directly or indirectly)the LB film 30 to the self-assembled molecular film 29.

Referring now to FIG. 4G, the method optionally includes establishing apolymer film 40 on the LB film 30 of the molecular layer 21. Theaddition of the polymer film 40 may be desired or required because thetop electrode or substrate 38 materials may react with and/or penetrateor diffuse through the LB film 30, even though the LB film 30 issubstantially densely packed and uniform. It is believed, without beingbound to any theory, that the polymer film 40 has molecules that arelarger in size and may be cross-linked, thus acting as an effectivebarrier against reaction and/or penetration or diffusion. It is to beunderstood that the polymer film 40 may be designed to contain moietiesthat will react with the metal and form a protective layer of material,such as titanium nitride, titanium carbide, titanium oxide, aluminumoxide, aluminum nitride, aluminum carbide, or mixtures thereof, or thelike, that will prevent further metal diffusion and act as a barrier todiffusion of oxygen and/or water.

It is desirable that a suitable polymer film 40 be compatible with (i.e.form a strong bonding interaction via ionic attractions, hydrogenbonding, van de Waals forces or explicit covalent chemical bonds formedbetween the LB film 30 and the polymer side groups) both the topelectrode or substrate 38 that it will contact and the LB film 30 of themolecular layer 21. In an embodiment, the polymer film 40 may includeconducting polymers. For example, the polymer film 40 may include, butis not limited to, doped polyanaline, undoped polyaniline, substitutedpolyaniline, doped polypyrrole, undoped polypyrrole, substitutedpolypyrrole, doped polythiophene, undoped polythiophene, substitutedpolythiophene, doped polyisothianaphthene, undoped polyisothianaphthene,substituted polyisothianaphthene, doped polyparaphenylene, undopedpolyparaphenylene, substituted polyparaphenylene, doped polythienylenevinylene, undoped polythienylene vinylene, substituted polythienylenevinylene, doped polyparaphenylene vinylene, undoped polyparaphenylenevinylene, substituted polyparaphenylene vinylene, doped polyacetylene,undoped polyacetylene, substituted polyacetylene, or mixtures thereof.Examples of suitable dopants include, but are not limited to anilines,titanium chlorides, boron fluorides, boron chlorides, aluminumchlorides, ferric chlorides, iodine, sulfuric acids, or mixturesthereof.

Any suitable technique may be used to establish the polymer film 40. Inan embodiment, the polymer film 40 is established by one of spincasting, evaporation and sublimation. To obtain the desired thickness ofthe polymer film 40 via spin casting, a low concentration of polymer maybe dispersed in a solution having either a suitable solvent or a monomerof the polymer and a suitable initiating agent. This solution may thenbe spin cast followed by mild heat and/or vacuum treatment tosubstantially ensure even film formation.

Evaporative or sublimation techniques may require depositing acontrolled amount of the polymer (a non-limitative example of whichincludes a short chain version of the polymer to ensure a sufficientvapor pressure) or monomer onto the surface of the top electrode orsubstrate 38 or onto the LB film 30. If desired, the polymer chainlengths may be increased by including an initiator, and cross-linkingmay be achieved with some type of cross linking agent. The polymer film40 may then be subjected to heating or other curing processes that arecompatible with the molecular layer 21.

After establishing the polymer film 40, the top electrode or substrate38 may then be deposited thereon, as depicted in FIG. 4H.

An embodiment of a crossed wire molecular device 24 includes a pluralityof bottom electrodes 23, a plurality of top electrodes 38 crossing thebottom electrodes 23 at a non-zero angle, a self-assembled molecularfilm 29 formed from a plurality of active device molecules 18 bonded tothe bottom electrode 23, and an LB film 30 bonded to the self-assembledmolecular film 29. Each of the active device molecules 18 has amolecular switching moiety (MD) 26, and a linking group (LG) 27 and aself-assembling connecting group bonded to opposed ends of the moiety(MD) 26. The self-assembled molecular film 29 has one or more defectsite(s) 31 therein. Further, the LB film 30 is bonded to theself-assembled molecular film 29 via at least some of the linking groups(LG) 27 such that the active device molecules 18 and the defect site(s)31 are substantially covered. The films 29, 30 are operatively disposedin at least one junction formed where one electrode 23, 38 crossesanother electrode 38, 23; and the LB film 30 is chemically bonded on asurface of one of the plurality of top electrodes 38.

A non-limitative embodiment of a method of forming the crossed wiremolecular device 24 is as follows. The self-assembled molecular film 29is chemically bonded to the surface of at least one of the plurality ofbottom electrodes 23. An LB film 30 is formed and connected (viachemical and/or physical bonding) to at least some of the linking groups(LG) 27 of the active device molecules 18. The LB film 30 covers theplurality of active device molecules 18 and the one or more defectsite(s) 31 to form the molecular layer 21. The method may furtherinclude forming one of the plurality of top electrodes 38, and crossingthe one of the plurality of bottom electrodes 23 at the non-zero angle,thereby forming the junction therebetween. The molecular layer 21 isthereby operatively disposed at the junction.

An embodiment of a molecular switching device includes at least onebottom electrode 23 and at least one top electrode 38 crossing thebottom electrode 23 at a non-zero angle, thereby forming a junctionthere between. An embodiment of the molecular layer 21 (as describedherein) may be operatively disposed in the junction.

While several embodiments have been described in detail, it will beapparent to those skilled in the art that the disclosed embodiments maybe modified. Therefore, the foregoing description is to be consideredexemplary rather than limiting.

1. A method of forming a molecular layer, comprising the steps of:chemically bonding a self-assembled molecular film to a surface of asubstrate, the self-assembled molecular film including at least onedefect site and a plurality of active device molecules, each of theplurality of active device molecules including a molecular switchingmoiety having a self-assembling connecting group at one end of themoiety and a linking group at an opposed end of the moiety; forming aLangmuir-Blodgett (LB) film of a molecule on at least one of awater/solvent interface and an air/water interface, the moleculeincluding a moiety having first and second connecting groups at opposedends of the moiety; and connecting the LB film to at least some of thelinking groups of the plurality of active device molecules via arespective number of the first connecting groups, wherein the LB filmcovers the plurality of active device molecules and the at least onedefect site, thereby forming the molecular layer.
 2. The method asdefined in claim 1, further comprising the step of establishing apolymer film on the LB film, and wherein the molecule moiety is amolecular switching moiety.
 3. The method as defined in claim 2 whereinthe polymer film comprises at least one of doped polyanaline, undopedpolyaniline, substituted polyaniline, doped polypyrrole, undopedpolypyrrole, substituted polypyrrole, doped polythiophene, undopedpolythiophene, substituted polythiophene, doped polyisothianaphthene,undoped polyisothianaphthene, substituted polyisothianaphthene, dopedpolyparaphenylene, undoped polyparaphenylene, substitutedpolyparaphenylene, doped polythienylene vinylene, undoped polythienylenevinylene, substituted polythienylene vinylene, doped polyparaphenylenevinylene, undoped polyparaphenylene vinylene, substitutedpolyparaphenylene vinylene, doped polyacetylene, undoped polyacetylene,substituted polyacetylene, and mixtures thereof.
 4. The method asdefined in claim 3 wherein the polymer film is doped with at least oneof anilines, titanium chlorides, boron fluorides, boron chlorides,aluminum chlorides, ferric chlorides, iodine, sulfuric acids, andmixtures thereof.
 5. The method as defined in claim 2 whereinestablishing is accomplished by one of spin casting, evaporation, andsublimation.
 6. The method as defined in claim 1 wherein connecting theLB film to the at least some linking groups is accomplished by one ofchemical bonding and physical bonding.
 7. The method as defined in claim6 wherein chemical bonding is one of ionic bonding, covalent bonding andcoordination bonding.
 8. The method as defined in claim 7 whereincovalent bonding is accomplished by one of oxidative cross-linking,heat-initiated cross-linking, photo-initiated cross-linking,substitution reactions, esterification, and amide formation.
 9. Themethod as defined in claim 6 wherein physical bonding is one of hydrogenbonding and van der Waals force.
 10. The method as defined in claim 1wherein the linking group and the first and second connecting groupscomprise at least one of multivalent hetero atoms selected from thegroup consisting of C, N, O, S, and P; functional groups containing thehetero atoms and selected from the group consisting of NH₂, NH-alkyl,NH-acyl, and NH-aryl; pyridine; substituted pyridines; heterocycliccompounds including at least one nitrogen atom; carboxylic acids;carboxylic esters; amides; nitrites; sulfuric acids; phosphoric acids;saturated hydrocarbons; unsaturated hydrocarbons; heterocyclic systems;amines; alkyl amines; and mixtures thereof.
 11. The method as defined inclaim 1 wherein the self-assembling connecting group comprises at leastone of multivalent hetero atoms selected from the group consisting of C,N, O, S, and P; functional groups containing the hetero atoms andselected from the group consisting of SH, S-acyl, S—S-alkyl, OH, NH₂,NH-alkyl, NH-aryl, NH-acyl; heterocyclic compounds; pyridine;substituted pyridines; carboxylic acids; carboxylic esters; amides;nitrites; amines; alkyl amines; and mixtures thereof.
 12. The method asdefined in claim 1 wherein the molecular switching moiety having aself-assembling connecting group at one end of the moiety and a linkinggroup at an opposed end of the moiety is at least one of an opticallyswitchable molecular functional unit and an electrically switchablemolecular functional unit.
 13. The method as defined in claim 12 whereinthe molecular switching moiety having a self-assembling connecting groupat one end of the moiety and a linking group at an opposed end of themoiety comprises at least one of saturated hydrocarbons, unsaturatedhydrocarbons, substituted hydrocarbons, heterocyclic systems,organometallic complex systems, and mixtures thereof.
 14. The method asdefined in claim 1 wherein the substrate is a bottom electrode.
 15. Themethod as defined in claim 14, further comprising the step of depositinga top electrode on the LB film.
 16. A method of forming a crossed wiremolecular device comprising a plurality of bottom electrodes, aplurality of top electrodes crossing the bottom electrodes at a non-zeroangle, a self-assembled molecular film chemically bonded to a surface ofeach of the bottom electrodes, the self-assembled molecular filmincluding at least one defect site and a plurality of active devicemolecules, each of the plurality of active device molecules including amolecular switching moiety having a self-assembling connecting group atone end of the moiety and a linking group at an opposed end of themoiety, and an LB film connected to at least some of the linking groupsof the plurality of active device molecules, the self-assembledmolecular film and the LB film operatively disposed in at least onejunction formed where one electrode crosses another electrode, themethod comprising the steps of: chemically bonding the self-assembledmolecular film to the surface of each of the plurality of bottomelectrodes; forming a Langmuir-Blodgett (LB) film of a molecule on atleast one of a water/solvent interface and an air/water interface, themolecule including a molecular switching moiety having first and secondconnecting groups at opposed ends of the moiety; connecting the LB filmto at least some of the linking groups of the plurality of active devicemolecules via a respective number of the first connecting groups,wherein the LB film covers the plurality of active device molecules andthe at least one defect site; and forming one of the plurality of topelectrodes, crossing the one of the plurality of bottom electrodes atthe non-zero angle, thereby forming the at least one junctiontherebetween, wherein the LB film is chemically bonded on a surface ofthe one of the plurality of top electrodes.
 17. The method as defined inclaim 16, further comprising the step of establishing a polymer film onthe LB film prior to forming the one of the plurality of top electrodes.18. The method as defined in claim 17 wherein the polymer film comprisesat least one of doped polyanaline, undoped polyaniline, substitutedpolyaniline, doped polypyrrole, undoped polypyrrole, substitutedpolypyrrole, doped polythiophene, undoped polythiophene, substitutedpolythiophene, doped polyisothianaphthene, undoped polyisothianaphthene,substituted polyisothianaphthene, doped polyparaphenylene, undopedpolyparaphenylene, substituted polyparaphenylene, doped polythienylenevinylene, undoped polythienylene vinylene, substituted polythienylenevinylene, doped polyparaphenylene vinylene, undoped polyparaphenylenevinylene, substituted polyparaphenylene vinylene, doped polyacetylene,undoped polyacetylene, substituted polyacetylene, and mixtures thereof.19. The method as defined in claim 18 wherein the polymer film is dopedwith at least one of anilines, titanium chlorides, boron fluorides,boron chlorides, aluminum chlorides, ferric chlorides, iodine, sulfuricacids, and mixtures thereof.
 20. The method as defined in claim 17wherein establishing is accomplished by one of spin casting, evaporationand sublimation.
 21. The method as defined in claim 16 whereinconnecting the LB film to the at least some linking groups isaccomplished by one of chemical bonding and physical bonding.
 22. Themethod as defined in claim 21 wherein chemical bonding is one of ionicbonding, covalent bonding and coordination bonding.
 23. The method asdefined in claim 22 wherein covalent bonding is accomplished by one ofoxidative cross-linking, heat-initiated cross-linking, photo-initiatedcross-linking, substitution reactions, esterification, and amideformation.
 24. The method as defined in claim 21 wherein physicalbonding is one of hydrogen bonding and van der Waals force.
 25. Themethod as defined in claim 16 wherein the linking group and the firstand second connecting groups comprise at least one of multivalent heteroatoms selected from the group consisting of C, N, O, S, and P;functional groups containing the hetero atoms and selected from thegroup consisting of NH₂, NH-alkyl, NH-acyl, and NH-aryl; pyridine;substituted pyridines; heterocyclic compounds including at least onenitrogen atom; carboxylic acids; carboxylic esters; amides; nitriles;sulfuric acids; phosphoric acids; saturated hydrocarbons; unsaturatedhydrocarbons; heterocyclic systems; amines; alkyl amines; and mixturesthereof.
 26. The method as defined in claim 16 wherein theself-assembling connecting group comprises at least one of multivalenthetero atoms selected from the group consisting of C, N, O, S, and P;functional groups containing the hetero atoms and selected from thegroup consisting of SH, S-acyl, S—S-alkyl, OH, NH₂, NH-alkyl, NH-aryl,NH-acyl; heterocyclic compounds; pyridine; substituted pyridines;carboxylic acids; carboxylic esters; amides; nitriles; amines; alkylamines; and mixtures thereof.
 27. The method as defined in claim 16wherein the molecular switching moiety having a self-assemblingconnecting group at one end of the moiety and a linking group at anopposed end of the moiety; and the molecular switching moiety havingfirst and second connecting groups at opposed ends of the moiety areeach at least one of an optically switchable molecular functional unitand an electrically switchable molecular functional unit.
 28. The methodas defined in claim 27 wherein each of the molecular switching moietiescomprises at least one of saturated hydrocarbons, unsaturatedhydrocarbons, substituted hydrocarbons, heterocyclic systems,organometallic complex systems, and mixtures thereof.
 29. A molecularlayer comprising: a Langmuir-Blodgett (LB) film of a molecule connectedto a self-assembled molecular (SAM) film including a plurality of activedevice molecules, the molecule including a molecular switching moietyhaving first and second connecting groups at opposed ends of the moiety,each of the plurality of active device molecules including: a switchingmoiety; a self-assembling connecting group at one end of the switchingmoiety; and a linking group at an opposed end of the switching moiety;and at least one defect site in the SAM film, the defect disposedbetween at least two of the plurality of active device molecules;wherein a respective number of the first connecting groups of the LBfilm are connected to at least some of the plurality of active devicemolecules via the linking groups; and wherein the LB film covers theplurality of active device molecules and the at least one defect site.30. The molecular layer as defined in claim 29, further comprising apolymeric film established on the LB film.
 31. The molecular layer asdefined in claim 30 wherein the polymer film comprises at least one ofdoped polyanaline, undoped polyaniline, substituted polyaniline, dopedpolypyrrole, undoped polypyrrole, substituted polypyrrole, dopedpolythiophene, undoped polythiophene, substituted polythiophene, dopedpolyisothianaphthene, undoped polyisothianaphthene, substitutedpolyisothianaphthene, doped polyparaphenylene, undopedpolyparaphenylene, substituted polyparaphenylene, doped polythienylenevinylene, undoped polythienylene vinylene, substituted polythienylenevinylene, doped polyparaphenylene vinylene, undoped polyparaphenylenevinylene, substituted polyparaphenylene vinylene, doped polyacetylene,undoped polyacetylene, substituted polyacetylene, and mixtures thereof.32. The molecular layer as defined in claim 31 wherein the polymer filmis doped with at least one of anilines, titanium chlorides, boronfluorides, boron chlorides, aluminum chlorides, ferric chlorides,iodine, sulfuric acids, and mixtures thereof.
 33. The molecular layer asdefined in claim 29 wherein the LB film is connected to the plurality ofactive device molecules via one of ionic bonding, covalent bonding,coordination bonding, hydrogen bonding and van der Waals force.
 34. Themolecular layer as defined in claim 29 wherein the linking group and thefirst and second connecting groups comprise at least one of multivalenthetero atoms selected from the group consisting of C, N, O, S, and P;functional groups containing the hetero atoms and selected from thegroup consisting of NH₂, NH-alkyl, NH-acyl, and NH-aryl; pyridine;substituted pyridines; heterocyclic compounds including at least onenitrogen atom; carboxylic acids; carboxylic esters; amides; nitriles;sulfuric acids; phosphoric acids; saturated hydrocarbons; unsaturatedhydrocarbons; heterocyclic systems; amines; alkyl amines; and mixturesthereof.
 35. The molecular layer as defined in claim 29 wherein theself-assembling connecting group comprises at least one of multivalenthetero atoms selected from the group consisting of C, N, O, S, and P;functional groups containing the hetero atoms and selected from thegroup consisting of SH, S-acyl, S—S-alkyl, OH, NH₂, NH-alkyl, NH-aryl,NH-acyl; heterocyclic compounds; pyridine; substituted pyridines;carboxylic acids; carboxylic esters; amides; nitrites; amines; alkylamines; and mixtures thereof.
 36. The molecular layer as defined inclaim 29 wherein the switching moiety of the plurality of active devicemolecules; and the molecular switching moiety having first and secondconnecting groups at opposed ends of the moiety are each at least one ofan optically switchable molecular functional unit and an electricallyswitchable molecular functional unit.
 37. The molecular layer as definedin claim 36 wherein each of the switching moiety and the molecularswitching moiety comprises at least one of saturated hydrocarbons,unsaturated hydrocarbons, substituted hydrocarbons, heterocyclicsystems, organometallic complex systems, and mixtures thereof.
 38. Amolecular switching device, comprising: at least one bottom electrode;at least one top electrode, the top electrode crossing the bottomelectrode at a non-zero angle, thereby forming a junction; and amolecular layer operatively disposed in the junction, the molecularlayer including: a plurality of active device molecules each having aswitching moiety, a self-assembling connecting group at one end of themoiety and a linking group at an opposed end of the moiety; at least onedefect site between the plurality of active device molecules; and aLangmuir-Blodgett (LB) film of a molecule connected to at least some ofthe linking groups, the molecule including a switching moiety havingfirst and second connecting groups at opposed ends of the moiety,wherein a respective number of the first connecting groups of the LBfilm are connected to the plurality of active device molecules via theat least some of the linking groups, and wherein the LB film covers theplurality of active device molecules and the at least one defect site.39. The molecular switching device as defined in claim 38, furthercomprising a polymeric film established on the LB film.
 40. Themolecular switching device as defined in claim 39 wherein the polymerfilm comprises at least one of doped polyanaline, undoped polyaniline,substituted polyaniline, doped polypyrrole, undoped polypyrrole,substituted polypyrrole, doped polythiophene, undoped polythiophene,substituted polythiophene, doped polyisothianaphthene, undopedpolyisothianaphthene, substituted polyisothianaphthene, dopedpolyparaphenylene, undoped polyparaphenylene, substitutedpolyparaphenylene, doped polythienylene vinylene, undoped polythienylenevinylene, substituted polythienylene vinylene, doped polyparaphenylenevinylene, undoped polyparaphenylene vinylene, substitutedpolyparaphenylene vinylene, doped polyacetylene, undoped polyacetylene,substituted polyacetylene, and mixtures thereof.
 41. The molecularswitching device as defined in claim 40 wherein the polymer film isdoped with at least one of anilines, titanium chlorides, boronfluorides, boron chlorides, aluminum chlorides, ferric chlorides,iodine, sulfuric acids, and mixtures thereof.
 42. The molecularswitching device as defined in claim 38 wherein the LB film is connectedto the plurality of active device molecules via one of ionic bonding,covalent bonding, coordination bonding, hydrogen bonding and van derWaals force.
 43. The molecular switching device as defined in claim 38wherein the linking group and the first and second connecting groupscomprise at least one of multivalent hetero atoms selected from thegroup consisting of C, N, O, S, and P; functional groups containing thehetero atoms and selected from the group consisting of NH₂, NH-alkyl,NH-acyl, and NH-aryl; pyridine; substituted pyridines; heterocycliccompounds including at least one nitrogen atom; carboxylic acids;carboxylic esters; amides; nitriles; sulfuric acids; phosphoric acids;saturated hydrocarbons; unsaturated hydrocarbons; heterocyclic systems;amines; alkyl amines; and mixtures thereof.
 44. The molecular switchingdevice as defined in claim 38 wherein the self-assembling connectinggroup comprises at least one of multivalent hetero atoms selected fromthe group consisting of C, N, O, S, and P; functional groups containingthe hetero atoms and selected from the group consisting of SH, S-acyl,S—S-alkyl, OH, NH₂, NH-alkyl, NH-aryl, NH-acyl; heterocyclic compounds;pyridine; substituted pyridines; carboxylic acids; carboxylic esters;amides; nitriles; amines; alkyl amines; and mixtures thereof.
 45. Themolecular switching device as defined in claim 38 wherein the switchingmoiety; and the switching moiety having first and second connectinggroups at opposed ends of the moiety are each at least one of anoptically switchable molecular functional unit and an electricallyswitchable molecular functional unit.
 46. The molecular switching deviceas defined in claim 45 wherein each of the switching moieties compriseat least one of saturated hydrocarbons, unsaturated hydrocarbons,substituted hydrocarbons, heterocyclic systems, organometallic complexsystems, and mixtures thereof.